Problem: Solve for $x$ : $9\sqrt{x} - 4 = 2\sqrt{x} + 9$
Answer: Subtract $2\sqrt{x}$ from both sides: $(9\sqrt{x} - 4) - 2\sqrt{x} = (2\sqrt{x} + 9) - 2\sqrt{x}$ $7\sqrt{x} - 4 = 9$ Add $4$ to both sides: $(7\sqrt{x} - 4) + 4 = 9 + 4$ $7\sqrt{x} = 13$ Divide both sides by $7$ $\frac{7\sqrt{x}}{7} = \frac{13}{7}$ Simplify. $\sqrt{x} = \dfrac{13}{7}$ Square both sides. $\sqrt{x} \cdot \sqrt{x} = \dfrac{13}{7} \cdot \dfrac{13}{7}$ $x = \dfrac{169}{49}$